fix: when reasoningEffort = "", no "reasoning" field

model.go

@@ -14,16 +14,16 @@ type OpenaiChatCompletionReq struct {
 }
 
 type OpenaiResponseReasoning struct {
-	Effort  string `json:"effort"`
+	Effort  string `json:"effort,omitempty"`
 	Summary string `json:"summary,omitempty"` // auto, concise, detailed
 }
 
 type OpenaiChatResponseReq struct {
-	Model       string                  `json:"model"`
-	Input       []OpenaiChatMessage     `json:"input"`
-	Temperature *float64                `json:"temperature,omitempty"`
-	Reasoning   OpenaiResponseReasoning `json:"reasoning,omitempty"`
-	Stream      bool                    `json:"stream"`
+	Model       string                   `json:"model"`
+	Input       []OpenaiChatMessage      `json:"input"`
+	Temperature *float64                 `json:"temperature,omitempty"`
+	Reasoning   *OpenaiResponseReasoning `json:"reasoning,omitempty"`
+	Stream      bool                     `json:"stream"`
 }
 
 type OpenaiResponseStreamEvent struct {

openai-response.go

@@ -32,10 +32,13 @@ func OpenaiStreamChatResponses(
 		Model:       model,
 		Input:       msgs,
 		Temperature: temperature,
-		Reasoning:   OpenaiResponseReasoning{Effort: reasoningEffort},
 		Stream:      true,
 	}
 
+	if reasoningEffort != "" {
+		body.Reasoning = &OpenaiResponseReasoning{Effort: reasoningEffort}
+	}
+
 	payload, err := json.Marshal(body)
 	if err != nil {
 		return nil, err